Most of the trucks that comprise a tractor and a trailer are equipped with an electricity supply source only in the tractor and the trailer does not have an independent electricity supply. The electricity supply of the trailer is in general from the tractor and the electricity interface or connection therebetween is achieved by a cable. For ready assembly and disassembly, the trailer connection cable is usually provided with a first type end connector (such as a plug) at each of two ends thereof and correspondingly, the tractor and the trailer are each provided with a mated second type end connector (such as a socket) to which the respective first type connector is releasably engaged so that a quick electrical connection may be established/released between the tractor and the trailer. The plug and the socket are mated connectors and the term "connector", as used herein, may be generically used to refer to both the plug and the mated socket. However, a plug will be used as an example to describe the present invention herein and it is understood that the principle of the present invention is also applicable to a socket.
FIG. 1 of the attached drawings illustrates an example of conventional plug structures of the trailer connection cable, comprising an insulation casing 10 having a plurality of bores 12 extending therethrough in an axial direction. Each of the bores 12 has a slot 14 formed on an inside surface thereof and extending in the axial direction along only a portion of the bore 12, preferably from one axial end of the plug to approximately axially middle of the plug, and thus not completely axially extending through the plug casing 10. A stop shoulder 16 is formed at the inner end of the slot 14.
A tubular conductor 18 is inserted in each of the bores 12, the tubular conductor 18 having an outside diameter substantially corresponding to inside diameter of the respective bore 12 to be receivable within the bore 12. A wire 20 is fixed to each of the tubular conductors 18 with a conductive core 22 of the wire 20 in electrical and physical engagement with the tubular conductor 18. The tubular conductors 18 are provided with a barb 24 that is receivable within the slot 14 of the respective bore 12 and anchored at the stop shoulder 16 of the slot 14. The barb 24 is formed in an inclined fashion to facilitate the insertion of the tubular conductor 18 into the respective bore 12 and, once the tubular conductor 18 is inserted into the bore 12, allows the barb 24 to engage the stop shoulder 16 which prevents the tubular conductor 18 from readily separating from the bore 12.
The tubular conductor 18 has an axially extending inner through hole having a diameter sized to receive a corresponding one of a number of terminal pins of a socket (not shown in the drawings) therein when the plug is mated with the socket and the tubular conductor 18 is made elastically deformable so as to provide a tight and secure engagement between the terminal pin (not shown) and the tubular conductor 18. An electrical connection is thus established between the conductive core 22 of the wire 20 and the terminal pin of the socket.
Conventionally, the tubular conductor 18 is made of a metal sheet by means of mechanical stamping operation to form the tubular configuration so that an axial slit is present between the two lateral edges of the metal sheet that are brought to meet each other in the formation of the tubular configuration. Due to the existence of the slit, mechanical fatigue frequently occurs after numerous cycles of insertion/withdrawal of the terminal pin of the socket into/out of the tubular conductor 18. Such a mechanical fatigue may result in an un-tight engagement between the terminal pin and the tubular conductor 18 which in turn causes poor electrical engagement therebetween.
The slot 14 of each of the bores 12 is arranged to extend to an axial end. of the casing 10 to allow a slender tool, such as a screw driver, to be inserted therein to depress the barb 24 radially inward for release the engagement of the barb 24 with the stop shoulder 16 of the slot 14 and thus allowing the tubular conductor 18 to be released from the bore 12.
A disadvantage of such a structure is that the barb 24 of the tubular conductor 18 has to be precisely aligned with the slot 14 of the respective bore 12 in mounting the tubular conductor 18 in the plug so that the barb 24 is received into the slot 14 and engages the stop shoulder 16 of the slot 14 when the tubular conductor 18 is inserted into the bore 12. Thus it is quite inconvenient in mounting the tubular conductor 18 into the casing 10.
Furthermore, in case that the plug is damaged and has to be replaced, although it is possible to release the tubular conductor 18 out of the casing 10 by inserting for example a screw driver into the slot 14, a difficulty arises that since the wire 20 is securely fixed to the tubular conductor 18 by means of plastic deformation of a portion of the tubular conductor 18 which "pinches" the conductive core 22 of the wire 20 on the tubular conductor 18, separating the tubular conductor 18 from the wire 20 is not so ready as to encourage a repairperson to attempt releasing the tubular conductor 18 from the wire 20 without cutting off the wire 20. Thus, generally, in repairing a damaged plug of the trailer connection cable, a replacement plug of different structure is used which is particularly shown in FIG. 2 of the attached drawings.
As shown in FIG. 2, which illustrates a cable plug particularly designed for repair of a damaged cable, which will be referred to as "renovation plug" hereinafter, the renovation plug comprises an insulation casing 26, similarly having a plurality of axially-extending through bores 28, each having an elongated conductor 30 fixed therein. The conductor 30 has two axial ends, each having a recessed cavity 32. One of the cavities 32 has a depth sufficient to receive the insertion of a terminal pin of the socket and the other cavity 32 is sized to receive the conductive core 22 of the wire 20 from which the damaged plug (or the tubular conductor 18 of the damaged plug) has been removed. The casing 26 also has a plurality of radially-extending holes 34, each in communication with one of the axial bores 28 and the conductor 30 that is fixed inside the bore 28 is also provided with a radial hole 35 substantially aligned with the respective radial hole 34 of the casing 26. The hole 35 is in communication with the cavity 32 of the conductor 30 that receives the conductive core 22 of the wire 20 therein and has an inner threading with which a screw 36 that extends through the radial hole 34 of the casing 26 engages to secure the conductive core 22 of the wire 20 in the cavity 32 of the conductor 30, thus establishing an electrical connection between the conductor 30 and the wire 20.
Thus, the plug that is used in a cable manufacturing factory has a structure different from that is used in repairing a damaged cable in a repairing workshop. One of the reasons for such a situation is that the cable manufacturing factory needs to handle a lot of cables and thus requires high efficiency which makes it impossible to use screws to fix the wires to the plug as that is adapted in the cable repairing workshop. The fact that different plug structures are respectively used by the manufacturing factory and the repairing workshop certainly causes problems to the cable parts manufacturers and suppliers.
Therefore, it is desirable to have a trailer connection cable plug structure which suits both the needs of the cable manufacturer and the cable repairing workshops and which is capable to simplify the manufacture of the trailer connection cable.